Direct compression methods and granule compression methods and the like are known examples of methods of producing solid preparations. Direct compression methods have fewer steps than granule compression methods, which require a granulation operation, and are also superior from the viewpoint of validation. However, direct compression methods are more readily affected by the properties of the powder, and therefore appropriate control of the powder properties of the principal agent and any additives, and appropriate selection of the production equipment and process are important factors from the viewpoint of achieving stable tablet production. Compression moldability can be particularly problematic in the direct compression method. If the compression moldability is low, then the tablets obtained upon molding tend to have low hardness and suffer from high friability. As a result, the tablets tend to be prone to damage during packaging and filling steps, and during transport. A binder is typically used to improve the compression moldability. However, there are very few compounds that can be used satisfactorily as a binder that can be used in a dry direct compression method and can generate appropriate bonding strength in a small amount.
Hydroxyalkylcellulose is used as a binder and molding base material for addition to solid preparations such as granules and tablets of medicines, as a binder for producing ceramics, as a coating agent for films, and as a viscosity modifier, dispersant or tackifier.
Hydroxyalkylcellulose is usually supplied in powder form. Spray dry methods have been reported as methods of preparing hydroxypropylcellulose particles. When a spray dry method is used, the particles must be prepared from a dilute solution in order to obtain the target particles, which is problematic from a productivity perspective. Further, Patent Document 1 discloses hydroxypropylcellulose particles having a particle size of 1 to 150 μm for use in a tacky layer for a patch. Further, Patent Document 2 and Patent Document 3 disclose low-substitution degree hydroxypropylcellulose particles for use in solid preparations, the particles having a volume-average particle size measured by a dry laser diffraction method of not more than 25 μm. These hydroxypropylcellulose particles are prepared as fluidized bed granules using a powder obtained from a vibration mill or the like.